Both leather animal hides and fabrics are used throughout the world today in the construction of consumer products. For example, leather and fabrics are popular coverings used in furniture and other consumer products. In today's economy, for furniture manufacturing to be profitable, the yield from leather hides and decorative fabrics used to cover the furniture needs to be optimized.
The popularity of leather is due to its durability, look and feel. Leather hides are also an expensive alternative, usually representing 2 to 4 times the cost of woven goods. Therefore, maximum yield and utilization of the leather hide is essential in controlling the manufacturing cost of products containing leather. This is quite difficult considering the irregularities of the leather hides which vary in both size and shape. Leather is also a natural product containing imperfections that must be taken into consideration when deciding where to cut certain parts for a product.
Both manual and mechanical methods currently exist for the cutting of leather hides while attempting to maximize leather yield.
Typical manual methods include the placement of hard (plastic or cardboard) templates on the leather hide. The leather is then typically marked with chalk, grease pencil, or other writing instruments using the template as a guide. After the entire hide is marked, the leather is then cut using a variety of knives, both powered and non-powered. Alternatively, sometimes the marking of the leather is omitted and the leather is cut using a non-powered rolling knife guided by following the edge of each template. Using these manual methods does not produce optimum leather yield since the manual marker or cutter generally does not attempt to place the templates in very many positions before marking or cutting. Typically, there are millions of feasible placement options for each template on a given leather hide and it is too time consuming to attempt placement at every possible location. It is also impossible to know if the placement of the templates at any given location represents the best yield for that particular leather hide.
Typical mechanical methods include the placement of the leather hide on a table or conveyor belt, which is part of an automated cutting machine. A person using one of two methods then defines imperfections in the leather hide. In some cases the leather hides are marked with a colored tape, chalk or grease pencil. Each color represents a different type of imperfection. Often, markings on the leather hide are difficult or impossible to remove. The glue on pinstripe tape may leave residue on the hide and can damage the appearance of the surface. In other cases, the leather hide is marked digitally using a laser pointer, sonic digitizer or a digitizing tablet underneath the cutting surface on the machine. After defect marking, the leather hide is photographed with a camera. A computer then processes the digitized image and the boundary or perimeter of the hide is determined and represented digitally by a closed polyline. The imperfections are also processed at the same time resulting in digital map of the imperfections and their relationship to the boundary of the leather hide. A computer uses the digitally defined leather hide data to try multiple iterations of digital template placement, taking into consideration imperfection types and locations. This is generally accomplished using various available software systems designed for nesting templates on leather hides. Nesting is usually performed for a specified length of time, for a specified number of iterations, or until a yield threshold has been met or exceeded. Once the nesting is complete, the digital template definitions and locations are converted to a numeric code format that is interpreted by the master control computer on the cutting machine. The machine using this digital data then cuts the leather hide.
While mechanical leather cutting systems of this type represent the best available method for achieving improved leather yields, they are quite expensive and costly to maintain. In addition, leather cutting machines do not represent a significant labor savings and their cost must be justified primarily on leather yield improvements alone.
With regards to decorative fabrics used to cover furniture, some of the same drawbacks apply to the methods of cutting patterns. With fabrics, fully automated pattern optimization and cutting systems are currently available. However, these automated systems are expensive and costly to maintain.